Endophytic Phyllosticta diversity in mangroves and its antimicrobial potential: Dominance of P. capitalensis

Endophytic fungi from mangrove are promising sources of bioactive compounds. This study investigated the diversity of Phyllosticta species isolated from six mangrove species in Tanzania and screened their antimicrobial potential. Fifteen Phyllosticta isolates were obtained and identified through morphological and multi-locus phylogenetic analysis (ITS, LSU, and TEF). Thirteen isolates (87%) were identified as P. capitalensis , confirming its dominance. Crude ethyl acetate extracts were prepared from all isolates and screened for antimicrobial activity against Gram-positive ( Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633), Gram-negative ( Escherichia coli ATCC 8739), and fungal ( Candida albicans ATCC 10231) pathogens using disc diffusion and broth micro dilution assays. Five extracts (33%) showed antimicrobial activity, with Sonneratia alba -derived isolate HMT153 showing the strongest broad-spectrum inhibition including against S. aureus (MIC = 0.39 mg/mL). This study represents the first report of endophytic Phyllosticta diversity and antimicrobial activity in Tanzanian mangroves, identifying P. capitalensis as the dominant and bioactive species and Sonneratia alba as a promising host for antimicrobial-producing endophytic strains